That is not possible in Firefox and also not recommended for safety reasons. When you save the file to the hard drive then your anti-virus software can scan the file when you launch it.

I had the option just before changing to my new PC so it is possible. I copied the Firefox profile from the old PC and the same happens so I suppose it's not related to Firefox but to a WIndows configuration.

There is an extension that makes this possible if you are willing to take the risk. You will have to check if this still works in Firefox 54.0.1.

• OpenDownload²: https://addons.mozilla.org/firefox/addon/opendownload-10902/